We are studying molecular mechanisms of replication and recombination in herpes simplex virus type-1 (HSV-1). HSV-1 serves as an excellent system in which to study DNA transactions. Hence, like eukaryotic chromosomes, the HSV-1 genome contains multiple origins of replication. Replication of the HSV-1 genome is mediated by the concerted action of several virus-encoded proteins that are thought to assemble into a multiprotein complex. Several host-encoded factors have also been implicated in viral DNA replication. Furthermore, replication of the HSV-1 genome is known to be closely associated with homologous recombination which may function in replication of genomic termini, in initiation of DNA replication and in maintaining genome stability. HSV-1 is also the prototypic herpesvirus and therefore serves as a model to understand the mechanism of replication of this class of virus. In this regard, HSV-1 is one of eight human herpesviruses that are know to cause diverse diseases ranging from cold sores and chicken pox to mononucleosis and even cancer. The high incidence of herpesviruses in the human population and the increased susceptibility of immuno-compromised individuals to these viruses make them a very important public health problem. HSV-1 in particular is the cause of oro-labial lesions as well as more serious encephalitis and cornea! blindness. In this grant period, we propose to examine aspects of viral recombination and its role in the viral replicative cycle, how viral replication initiates at an origin, and how leading and lagging strand synthesis are coordinated at the viral replication fork. Collectively, the proposed studies will provide novel insight into the replication of this medically important and biologically fascinating virus. They will also increase our overall knowledge of fundamental mechanisms in replication and recombination.